Bottle base to cover street as paving material (9)
I believe the answer is:
flagstone
'paving material' is the definition.
(thesaurus)
'bottle base to cover street' is the wordplay.
'bottle' becomes 'flagon' (I've seen this before).
'base' becomes 'e' (Euler's number - base of natural logarithms).
'to cover' means one lot of letters goes inside another.
'street' becomes 'st' (abbreviation).
'flagon'+'e'='flagone'
'flagone' placed around 'st' is 'FLAGSTONE'.
'as' acts as a link.
(Other definitions for flagstone that I've seen before include "Paving slab" , "One walked on" , "Fine-textured rock" , "It'll lay (some say) at ground level" , "Paving-slab" .)